2020-12-10 12:37:10 -06:00
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import streams, input_helpers, algorithm, sequtils, math
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2020-12-09 09:44:13 -06:00
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proc part1*(s: Stream): int =
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2020-12-10 01:08:23 -06:00
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var d1 = 0
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var d3 = 1
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var nums = @[0].concat(toSeq(s.asInts).sorted)
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for i in 1..<nums.len:
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case nums[i] - nums[i-1]:
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of 1: inc d1
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of 3: inc d3
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else: discard
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d1 * d3
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2020-12-09 09:44:13 -06:00
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proc part2*(s: Stream): int =
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2020-12-10 12:37:10 -06:00
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result = 1
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var nums = @[0].concat(toSeq(s.asInts).sorted)
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nums = nums.concat @[nums.max + 3]
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var l,r = 0
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while l < nums.len:
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r = l
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while r < (nums.len-1) and nums[r+1] - nums[r] == 1: inc r
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let ln = r+1-l
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case ln:
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of 0..2: discard
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of 3: result *= 2
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else: result *= 1 + (ln - 2) + (ln - 2).fac.div(2)
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l = r + 1
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# needed the tests on this one - math was a doozy
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const t2 = "1\n4\n5\n6\n7\n10\n11\n12\n15\n16\n19".newStringStream().part2()
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const t = ("1\n2\n3\n4\n7\n8\n9\n10\n11\n14\n17\n18\n19\n20\n23\n24\n25\n" &
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"28\n31\n32\n33\n34\n35\n38\n39\n42\n45\n46\n47\n48\n49").newStringStream().part2()
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doAssert 8 == t2
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doAssert 19208 == t
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